Hi all…the ‘Guideline Technical Document: Cyanobacterial Toxins’ is now available on Health Canada’s web site. “A seasonal maximum acceptable concentration (MAC) of 0.0015 mg/L (1.5 μg/L) is established for total microcystins in drinking water. This guideline is considered to be protective of the general population, including young children.”

I noted a couple of things that could be overlooked with a quick read:

  1. The guideline is qualified by the use of the word “seasonal”; however, it is not defined (other than being from spring to fall). This has implications for initiating and discontinuing sampling and frequency. Some guidance is provided.
  2. As opposed to targeting microcystin-LR (MC-LR), ‘total’ microcystins are specified, so while methods for some of the close to 100 microcystin variants are not yet available, or require instrumentation beyond the financial/analytical capacity of municipal or accredited labs, there appears to be an expectation that drinking water providers be aware of new analytical developments. While MC-LR is relatively commonly detected, other variants can be present, sometimes in higher concentrations than MC-LR.
  3. In Section 2.3 it is stated that “Analysis should be conducted for all of the measurable microcystin variants that are both dissolved in the water and bound within the cyanobacterial cells using a laboratory validated method.” This could be more challenging than analyzing only for dissolved variants.
  4. While the guideline is entitled “Guideline Technical Document: Cyanobacterial Toxins’, guidelines were not established for other cyanotoxins. This was qualified by indicating health and exposure data on anatoxin-a and cylindrospermopsin are limited. It would not be surprizing to see guidelines or regulations for cylindrospermopsin at some point. While anatoxin-a is another important cyanotoxin it might not meet the threshold for widespread occurrence that is typically needed for regulation (at least at the federal level).

The guideline contains a lot of good information on cyanobacteria and their toxins. It’s definitely worth a read if you want to get up to speed on the topic.

www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-guideline-technical-document-cyanobacterial-toxins.html

Bill

Guidelines for Canadian Drinking Water Quality: Guideline Technical Document

March 2017

Cyanobacterial toxins 

Part I. Overview and Application 

“1.0 Guideline 

A seasonal maximum acceptable concentration (MAC) of 0.0015 mg/L (1.5 μg/L) is established for total microcystins in drinking water. This guideline is considered to be protective of the general population, including young children. 

2.0 Executive summary 

Under the right environmental conditions, microcystins and other cyanobacterial toxins are naturally formed in water in the environment. They are produced and stored in the cells of cyanobacteria, and released when the cells rupture or die. Most scientific studies on cyanobacterial toxins focus on microcystins, which are generally regarded as the most important of the freshwater cyanotoxins.

This guideline technical document reviews and assesses the identified health risks associated with cyanobacterial toxins in drinking water. It assesses new studies and approaches and takes into consideration limitations in analytical methods and treatment technologies. Based on this review, the guideline for total microcystins in drinking water is established at a maximum acceptable concentration of 0.0015 mg/L (1.5 μg/L). Guidelines are not established for other cyanotoxins, including anatoxin-a and cylindrospermopsin, as health and exposure data on these toxins are limited.”